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PythonThinking/task2&3 课后练习及补充.md

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+# 1 基础 课后练习及补充
+
+
+
+## 1.1 数据类型相关练习
+
+
+
+### 1.1.1 数据类型转换
+  运行下面单元格，了解`int()`，`float()`，`str()`，`type()`等的用法
+
+
+
+```{code-block} python
+:linenos:
+
+# str -> int
+X = int('ABCD', 16)
+print(X)
+type(X)
+```
+
+```{code-block} python
+:linenos:
+
+# int -> float
+a = 520
+b = float(a)
+b
+```
+
+```{code-block} python
+:linenos:
+
+# float -> str
+a = 5.99
+b = str(a)
+b
+```
+
+  接下来，请尝试将字符串`'520'`转化为小数，可以使用`float()`
+```{code-block} python
+:linenos:
+
+a = '520'
+b = 
+```
+
+  运行下面单元格，了解字符串的切片操作
+```{code-block} python
+:linenos:
+
+a_string = 'Hello' + ' ' + "Women Who Code!"
+print(a_string)
+print("str[0]  :" + a_string[0])
+print("str[2:5]:" + a_string[2:5]) # Python speak: slicing
+print("str[2:] :" + a_string[2:])
+```
+
+## 1.2 列表操作
+
+  列表是个框，什么都可以往里装
+
+```{code-block} python
+:linenos:
+
+lis = [ "WWCode", 786 , 2.23, 'singapore', 70.2 ]
+print(lis[0:3])
+type(lis)
+```
+
+  列表的索引，先猜猜下面这个单元格能得到什么，再运行
+
+```{code-block} python
+:linenos:
+
+lis[0][2:]
+```
+
+  如果我想从lis里得到'sing'应该怎么做呢
+
+  列表的元素是可以修改的
+```{code-block} python
+:linenos:
+
+lis[2] = 3.3
+lis
+```
+  请尝试将列表最后一个元素更改为50
+
+  列表有一个非常好用的操作，叫list comprehension，可以运行下面单元格感受一下
+
+```{code-block} python
+:linenos:
+
+symbols = '$¢£¥€¤'
+codes = [ord(symbol) for symbol in symbols]
+codes
+```
+
+  `ord()`的作用是返回符号的unicode编码
+
+
+
+## 1.3 元组操作
+
+```{code-block} python
+:linenos:
+
+t1 = ( "WWCode", 100000 , 0.5 ) # org name, members, proportion of engineers
+t2 = 'Singapore', 1160.5
+t_singleton = ('We',) # singleton
+t_empty = ()
+print(type(t1)); print(type(t2))
+print(t_singleton);
+type(t_empty)
+```
+
+  元组元素不可修改，尝试运行下列代码
+```{code-block} python
+:linenos:
+
+t1[2] = 20
+```
+
+## 1.4 字典操作
+
+```{code-block} python
+:linenos:
+
+dict1 = {'name':'Women Who Code Singapore', 
+        'org':'WWCode', 
+        'city':'Singapore',
+        'members':1260}
+print(dict1['org'])
+type(dict1)
+```
+
+  字典元素可以更改
+
+  增加元素
+
+```python
+# 增加元素
+dict1['rank'] = 10
+```
+
+
+
+```python
+# 获取元素
+dict1['city']
+```
+
+
+
+```python
+# 获取不知是否存在的元素
+dict1.get('org','不存在')
+```
+
+
+
+```python
+dict1.get('ord','不存在')
+```
+
+
+
+## 1.5 Sets 集合  
+
+* Sets are a methematical concept, they are a lot like dictionaries with keys but no corresponding values. 
+* 跟数学的概念很相似，类似于字典的键，但没有对应的值
+* Sets are enclosed by curly braces, elements seperated by comma, '{','}'.  
+* 用花括弧
+* Sets do not support indexing or slicing, and do not have inherent order.  
+* 不支持下标应用和切片
+
+
+
+
+
+```python
+wwcode_asia_networks = {'Bangalore','Beijing','Chennai','Delhi','Gujarat','Hong Kong','Kuala Lumpur','Manila','Pune','Rajasthan','Shanghai','Singapore','Taipei','Tel-Aviv','Tokyo'}
+type(wwcode_asia_networks)
+```
+
+
+
+```python
+print(wwcode_asia_networks)
+```
+
+
+
+```python
+wwcode_asia_networks[1]
+```
+
+
+
+## 1.6 运算和布尔运算
+
+
+```{code-block} python
+:linenos:
+
+x = 1 + 2 # Addition
+y = 3 - 4 # Subtraction
+z = 5 * 6 # Multiplication
+a = z / y # Division
+b = z % x # Modulus
+c = y ** x # Exponent
+d = c // x # Floor Division
+print("x:" + str(x) + " y:" + str(y) + " z:" + str(z) + 
+      " a:" + str(a) + " b:" + str(b) + " c:" + str(c) + " d:" + str(d))
+```
+
+运算符|	描述|	实例
+-| :-: | -
+=	|简单的赋值运算符	|c = a + b 将 a + b 的运算结果赋值为 c
++=	|加法赋值运算符	|c += a 等效于 c = c + a
+-=	|减法赋值运算符	|c -= a 等效于 c = c - a
+*=	|乘法赋值运算符	|c *= a 等效于 c = c * a
+/=	|除法赋值运算符	|c /= a 等效于 c = c / a
+%=	|取模赋值运算符	|c %= a 等效于 c = c % a
+**=	|幂赋值运算符	|c \*\*= a 等效于 c = c \*\* a
+//=	|取整除赋值运算符	|c //= a 等效于 c = c // a
+
+  布尔运算和比较运算
+
+```{code-block} python
+:linenos:
+
+print(a == b) # equals
+print(a != b) # not equals
+print(a > b)  # greater than
+print(a < b)  # lesser than
+print(a >= b) # greater than or equal
+print(a <= b) # lesser than or equal
+```
+
+&emsp;&emsp;Logical Operators 逻辑运算符     
+&emsp;&emsp;and or not
+
+```python
+not True
+```
+
+
+
+```python
+not 0
+```
+
+
+
+```python
+not 4
+```
+
+
+
+```python
+3 < 4 < 5
+```
+
+
+
+```python
+3 < 4 < 2
+```
+
+
+
+```python
+3 < 4 and 4 < 5
+```
+
+
+
+```python
+3 < 5 or 8 > 5
+```
+
+```{code-block} python
+:linenos:
+
+a_string = "Women Who Code"
+print("Women" in a_string)
+print("Men" not in a_string)
+print(len("Women Who Code") is len(a_string))
+print(len("Hello World!") is not len(a_string))
+```
+
+
+```python
+# 判断闰年怎么判断呢
+year = 2100  # eval(input('输入年份（四位数）'))
+# 大家来试试
+```
+
+&emsp;&emsp;is 和  is not 运算符 与==以及!=的区别
+
+&emsp;&emsp;is 用于判断两个变量引用对象是否为同一个， == 用于判断引用变量的值是否相等。
+
+```{code-block} python
+:linenos:
+
+x = 5
+y = 5
+print(x == y)
+print(x is y)
+print(id(x))
+print(id(y))
+```
+
+```{code-block} python
+:linenos:
+
+help(id)
+```
+
+```{code-block} python
+:linenos:
+
+id(1)
+```
+
+```{code-block} python
+:linenos:
+
+id("abc")
+```
+
+```{code-block} python
+:linenos:
+
+id([1, 2, 3])
+```
+
+```{code-block} python
+:linenos:
+
+x = "abcabcabcabcabcabcabcabcabcabc"
+y = "abcabcabcabcabcabcabcabcabcabc"
+print(x == y)
+print(x is y)
+print(id(x))
+print(id(y))
+```
+
+```{code-block} python
+:linenos:
+
+# 数组比较
+x = [1, 2, 3]
+y = [1, 2, 3]
+print(x == y)
+print(x is y)
+print(id(x))
+print(id(y))
+```
+
+```{code-block} python
+:linenos:
+
+# 元组比较
+x = (1, 2, 3)
+y = (1, 2, 3)
+print(x == y)
+print(x is y)
+print(id(x))
+print(id(y))
+```
+
+```{code-block} python
+:linenos:
+
+# 字典比较
+x = {"id": 1, "name": "Tom", "age": 18}
+y = {"id": 1, "name": "Tom", "age": 18}
+print(x == y)
+print(x is y)
+print(id(x))
+print(id(y))
+```
+
+```{code-block} python
+:linenos:
+
+# 集合比较
+x = set([1, 2, 3])
+y = set([1, 2, 3])
+print(x == y)
+print(x is y)
+print(id(x))
+print(id(y))
+```
+
+```{code-block} python
+:linenos:
+
+# 赋值后比较
+x = [1, 2, 3]
+y = x
+print(x == y)
+print(x is y)
+print(id(x))
+print(id(y))
+```
+
+空值比较
+```{code-block} python
+:linenos:
+
+none_type = None
+none_type is None
+```
+
+## 1.A 附录 一些可能会用到的知识
+&emsp;&emsp;这部分内容在使用python的过程中可能会用得上，可以逐个运行单元格感受一下~
+
+### 1.A.1 Reserve Words保留字
+&emsp;&emsp;The following identifiers are used as reserved words of the language, and cannot be used as ordinary identifiers.
+&emsp;&emsp;一些关键字是系统自带的保留字，即不能用作为标识符
+
+```{code-block} python
+:linenos:
+
+import keyword
+keyword.kwlist
+```
+
+### 1.A.2 build-in functions内置函数
+&emsp;&emsp;这些函数不能作为变量名，可以作为函数直接调用，如：`print()` `input()`   
+`dir(\__builtins__)`可以看到内置函数列表
+
+```{code-block} python
+:linenos:
+
+dir(__builtins__)
+```
+
+```{code-block} python
+:linenos:
+
+aa = 3
+aaaa = 5
+dir()  #python内置函数；不带参数时，返回当前范围内的变量、方法和定义的类型列表
+        #带参数是，返回参数的属性、方法列表
+```
+
+```{code-block} python
+:linenos:
+
+help(dir)
+```
+
+```{code-block} python
+:linenos:
+
+help(print)   # 内置函数，查看函数或模块用途的详细说明
+```
+
+&emsp;&emsp;Hit the **STOP** square button in the button ribbons/bar on top to continue to next cell.
+
+```{code-block} python
+:linenos:
+
+#help(str)
+import copy
+help(copy.copy)
+```
+
+
+
+本篇整理：肖桐